A technique was disclosed in co-pending U.S. patent application Ser. No. 07/286,120, filed on Dec. 19, 1988, for fabricating grid structures of various configurations from a composite material consisting of fibers embedded in a matrix--e.g., graphite fibers embedded in an epoxy resin matrix.
A grid structure fabricated according to the technique disclosed in the aforementioned U.S. patent application Ser. No. 07/286,120 comprises intersecting grid sections, which define interstices of the grid structure. The intersecting grid sections interpenetrate each other without causing the integrity of any of the intersecting grid sections to be breached. Consequently, the technique disclosed in U.S. patent application Ser. No. 07/286,120 enables substantial uniformity in strength to be achieved without producing significant variations in weight distribution throughout the grid structure.
A grid structure according to the technique disclosed in the aforementioned U.S. patent application Ser. No. 07/286,120 is fabricated by the following procedure:
a) a filament made of fibrous material is arranged on a loom according to an iterative pattern so as to form intersecting grid sections, which define interstices of the grid structure that is to be fabricated;
b) filaments made of fibrous material are wound or wrapped around mandrels, which generally conform in cross-sectional configuration to the interstices defined by the intersecting grid sections;
c) the mandrels with the filaments of fibrous material wound or wrapped thereon are inserted into corresponding interstices of the grid structure;
d) the filament that is arranged on the loom so as to form the intersecting grid sections defining the interstices, as well as the filaments that are wound or wrapped around the mandrels inserted into the interstices, are impregnated with a liquid matrix material;
e) the filaments, after having been impregnated with the liquid matrix material, are then compressed between the mandrels in adjacent interstices;
f) the matrix material is then cured; and
g) the mandrels are removed from the interstices.
Intersecting grid sections defining the interstices of a grid structure that is fabricated according to the above-listed steps (as previously disclosed in U.S. patent application Ser. No. 07/286,120) can have planar or arcuate surfaces, depending upon the configuration of the loom and the mandrels. Prior to the present invention, however, no technique had ever been devised for imparting an undulate configuration to the surfaces of the intersecting grid sections defining the interstices of a grid structure.